it作形式主语的常见句型：
(1)It is+adj.+主语从句(用于此句型的形容词有：easy,hard,difficultpossible, important,impossible,neceseerybad.interesting,surprising等)
(2)It is+n.十主语从句(用于此句型中的词汇有：a pity,a shame,no wonder one's duty,fun,good manners,bad manners等)
(3)It is+及物动词的过去分词+that从句(此句型中常见的及物动词的过去分词有：said，told, known, reported, thought,believed, considered等)
(4)It十不及物动词+主语从句(此句型中常见的不及物动词有：seem，appear，the happen等）
①It is evident that the local government is trying tohelp the graduates with employment.省很明显，当地政府正试图帮助大学生就业。
②It's a pity that the research indicates that 81% of teachers are dissatisfied with their salary.遗憾的是，研究表明81%的教师对他们的薪水不满意。
③It's said that he is doing well in school.据说他在学校里表现很好。
④It seems that he is not willing to go there.看来他不愿意去那里。
